1. Field of the Invention
This invention relates to downhole well pumps and more particularly to well pumps powered by fluid pressure and to methods for using such pumps.
2. Description of the Prior Art
Downhole fluid powered pumps have been used for many years to lift production fluids from wells having insufficient bottom hole pressure to flow on their own. In most installations utilizing such fluid powered pumps, pressurized power fluid is conducted to the pump from the surface via a power fluid conduit extending exteriorly of and alongside the well tubing in which the pump is installed. Of course, if the well is equipped with a packer to seal the tubing-casing annulus below the pump, such annulus may be utilized to conduct power fluid to the pump, if desired. Such pump and installations are illustrated and described in my co-pending Application for Letters Patent for DOWNHOLE DOUBLE ACTING PUMP filed Jan. 7, 1983, Ser. No. 06/456,366, which application is a continuation application of my previously filed application, Ser. No. 06/152,529, filed May 22, 1980, now U.S. Pat. No. 4,405,291, which issued Sept. 20, 1983. Disclosed in these two prior applications is a double acting pump having two pump chambers which are axially aligned. A piston is reciprocable in each chamber, and they are connected together by a piston rod. The piston rod passes through a pilot valve mechanism positioned between the two chambers. Power fluid which may be gaseous or liquid, preferably compressed gas, enters the pump through a lateral port in its midsection, and the pilot valve directs such power fluid into each of the chambers alternately. As one of the pistons approaches the pilot valve mechanism, it engages the pilot valve and shifts it to the other of its two positions to direct the power fluid into the other chamber and to exhaust the first one. This spent power fluid is allowed to commingle with the pumped production fluids, and this aids in lifting them to the surface through the well tubing.
The present invention is an improvement over the apparatus of my co-pending application just discussed. This improved pump is particularly suitable for use in wells having small diameter casing since the power fluid conduit is located inside the tubing in which the pump is located, thus eliminating the danger of damaging the conduit.
Typical prior art downhole pump devices include the pump disclosed in U.S. Pat. No. 3,617,152 to Leslie L. Cummings. The pump of Cummings utilizes a compressed gaseous medium, such as gas or air, to displace well production fluids from the well and lift them to the surface. This pump is a single acting pump and requires relatively high pressure power gas in order to lift the well production fluids to the surface.
U.S. Pat. No. 4,084,923 to George K. Roeder discloses a downhole pump utilizing hydraulic fluid pressure for its operation. The pistons of the Roeder pump are driven by more than one engine, and a tubular piston rod supplies power fluid to a lower engine. Power oil may be conducted to the pump through a small conduit inside the well tubing, this being aided by the hollow piston rod.
It is desirable to provide a double acting downhole pump which can be run and pulled on a small diameter power fluid conduit, making such pump suitable for use in wells having casing so small that a suitable power fluid conduit cannot be placed in the tubing-casing annulus. It is further desirable to provide a remotely releasable connector for attaching such conduit to the pump, thus making it possible to release the conduit and remove it from the well without removing the pump.
The present invention overcomes the limitation of the double acting pump of my co-pending application as regards casing size since it can be run in tubing in wells having very small casing because the pump receives power fluid through a concentric conduit located in the tubing and attached to the upper end of the pump. This attachment is made by a remotely releasable connector enabling the pump and conduit to be run and/or pulled together or separately.